1. Field of the Invention
This invention relates to the field of seating and back systems and more particularly, to the field of seating and back systems for wheelchairs for growing children as well as adults whose bodies are changing as for example, due to weight gain or loss.
2. Discussion of the Background
Growing children present a unique problem to seating and backing systems for wheelchairs in that the fitting requirements of the child are continually changing sometimes even on a month-to-month basis. Consequently, a seating and back system that may properly position and support the growing child one month may not do so the next month or months. Such growth takes place in both the seat and back areas of the child; but, the primary fitting problem is presented in adjusting or modifying the seating portion of the system and in particular, the pre-ischial shelf area.
More specifically, a properly fitting seating system typically has a base seating member or cushion. The base member has a thigh supporting surface or shelf near its front and a step down to a depressed, seating well toward the rear which supports the child's buttocks including his or her ischial tuberosities. The child is preferably positioned with his or her ischial tuberosities (and the flesh immediately forward of them) immediately adjacent the face of the step. Ideally, the back of the child's knees are immediately adjacent the front surface of the seating member in roughly a 90 degree position with the child's feet on the footrests and the child's back is supported roughly in a 95 degree or so position. This aids in achieving maximum support under the thighs to reduce pressure under the ischial tuberosities and in achieving proper leg, pelvic, and spine positioning. However, with time, the child's thigh or femur bones will grow and lengthen often dramatically (e.g., 2 to 3 inches in 2 to 3 years). Although such growth is gradual, it manifests itself in the seating system in a number of ways. In particular, the previously proper fit of the child with the backs of his or her knees against the front of the seating member and his or her ischial tuberosities against the step face now finds the ischial tuberosities spaced rearwardly from the step face due to the femur growth. The end result is that the child often thrusts or scoots his buttocks forward until his or her ischial tuberosities again are immediately adjacent the step face. This can be due to a number of reasons including the fact that a child often lacks the discipline to sit up straight or may have involuntary extensor tone.
Such thrusting or scooting then misaligns the child's knees and legs which can lead to lower extremity deformities including abduction (legs permanently apart), adduction (legs permanently together), windsweeping (both legs permanently off to one side), or subluxation (dislocation) of the femur from the hip joint. Furthermore, such misalignments can lead directly to serious back problems, including permanent deformities, the most common of which is kyphosis or front-to-back curvature of the spine. Other back deformities include lordosis (excessive lumbar curve), and scoliosis (side-to-side curvature of the spine). These problems are further accentuated by the excessive muscle tone frequently found in people with spastic cerebral palsy. If such individuals are not properly positioned in their wheelchairs at every step of their growth process, the development of permanent deformity is frequent.
In the past, such fitting needs of a growing child were simply met by replacing the entire seating member with a larger one every 6 to 12 months. Such a process is obviously expensive. Further, in making such replacements in 6 to 12 month stages, the immediate fitting needs of the child at each stage were often not even met as the tendency was to compromise at each stage and to provide a larger than needed seating cushion in order to allow for some growth. Toward the end of any such stage, the fitting needs of the growing child were also usually not met as the tendency was to wait until the child had clearly overgrown the seating system before replacing it. In the meantime, seat belts, shoulder harnesses, and other restraints were often needed to maintain the child in the seating system not to mention the continuing discomfort and potential damage of such an ill-fitting seating system.
Another approach has been to use "linear" seating systems, consisting of plywood padded with foam. With these systems, the changing contours of the body did not significantly affect the fit of the seating, as substantial body contact was never achieved. Body contoured seating has been successfully developed for adults in wheelchairs (see, for example, applicant's U.S. Pat. Nos. 4,588,229, 4,726,624; and 5,018,790). These contoured systems have provided increased body contact, with a resulting increase in stability and positioning capability. This additional stability and contact have also been extremely effective in reducing the spasticity and tone that has pulled the child's bones into deformity. Such generic contours, particularly in a cushion, have been recognized to be of great value to children, but have been in limited use because as the child grew, the child invariably began sitting on the anti-thrusting shelf built into the contoured cushion. As a result, contoured seating has been used only minimally with children, with the effect that the individuals who most needed positioning were the ones least likely to receive it. In this regard, the reason children need positioning more than adults is that their bones are soft and are very susceptible to being pulled into permanent deformities, particularly during growth spurts.
With the above in mind, the seating and back systems of the present invention were developed. With them, a pre-ischial shelf extender or separate step means is provided wherein the seating cushion in the area of the ischial tuberosities can be selectively and progressively modified to accommodate the changing needs of the growing child. The basic, overall seating system of the present invention can then be used for a number of years in contrast to current seating systems that often need full replacements every few months. Additionally, the needs of a fully grown adult can also be met with the seating system of the present invention wherein an off-the-shelf or standard sized seating member can be easily and quickly modified and customized to specifically fit the adult. Adults whose bodies are changing (e.g., by weight gain or loss) or whose diagnoses are changing can also be accommodated. Other modifications and additions have also been made in the seating system of the present invention including a specially designed fluid pad. An adjustable back system was also specially developed for use with the seating system of the present invention; however, it can be used with other seating systems if desired. The adjustable back system permits the position of the back to be varied about multiple axes to meet the special needs of the child or adult user. The adjustable back system further includes unique features that provide a very desirable, low profile yet permit significant modes of adjustment.